Froth flotation



Paiented May 23, 1944 FROTH FLOTATION Kurt Felix Ruckwardt. Anaconda,Mont, as-

signor to Anaconda Copper Mining Company, a

corporation of Montana No Drawing. Application December 8, 1941,

Serial No. 422,103

8Claims. (claw- 16s This invention relates to froth flotation, and hasfor its principal object to provide an improved method for separating acopper sulphide from a lead sulphide by selective froth flotation.

Many zinc-lead sulphide ores contain copper sulphides, and many coppersulphide ores contain lead sulphides. It is common practice to separatezinc and lead sulphide minerals'by selective froth flotation, making alead concentrate low in zinc and a zinc concentrate low in lead Whencopper sulphides are present there is a decided tendency for th. copperto follow the lead. In the flotation of copper sulphide ores, leadsulphides, if present, follow the copper.

Copper in lead concentrate is undesirable in lead smelting, and a customlead smelter will pay very little for the copper in alead concentrate.Lead in a copper concentrate likewise laundesirable, as it largely goesinto fume and dust in smelting. for the most part cast into anodes forelectrolytic refining, and such anodes should not contain much lead. i

I have discovered that if an aqueous pulp containing a mixture of leadsulphides and copper sulphides is conditioned with a soluble phosphate,and the conditioned pulp is then subjected to a froth flotationoperation in the presence of a sulphide mineral collecting agent, the

Smelter-produced copper is bulk of the copper sulphide will float awayfrom v the bulk of the lead sulphidef The soluble phosphate appears todepress the lead sulp de Selec'tively, leaving the copper sulphide freto be floated; This effect probably is due to the formation of a minutelead phosphate film in the surface of the lead sulphide particles.

Based onthis discovery, the present invention provides an improvedmethod for separating a copper sulphide from a lead sulphide byselective froth flotation which comprises treating above about 8.0, andadvantageously between about 8 and 9. v

-It is preferable to condition the pulp with the soluble phosphate for aperiod of several minutes before adjusting the pH and subjecting thepulp to the flotation operation.

My investigations indicate that any soluble phosphate is suitable forconditioning the pulp preparatory to the selective flotation operation.A superphosphate fertilizer,- such, for example, as a treblesuperphosphate fertilizer, however, is a particularly economical andconvenient source of a soluble phosphate for conditioning the pulp. 1

The new method may be carried out as a single flotation operationresulting in production of a flotation concentrate containing the bulk.of the copper and a flotation tailing containing the bulk of the lead.Generally, however, it is best to employ separate rougher and cleanerflotation operations. In such operations,

the pulp, after conditioning with the soluble phosphate, and preferablyafter being made alkaline, is subjected to a rougher froth flotationoperation in the presence of a sulphide mineral collecting agent toproduce a tailing containing the bulk of the lead sulphide with butlittle of the copper sulphide and a concentrate contain-f ing the bulkof the copper sulphide with some lead sulphide. The concentrate soproduced is then advantageously conditioned with a further quantity of asoluble phosphate and is subjected to a cleaner froth flotationoperation, again in the presence of a sulphide mineral collecting agent,thus producing a cleaner concentrate containing the bulk of the coppersulphide with but little of the lead sulphide; and a tailing containlngmuch of the lead that accompanied the an aqueous pulp of the mixedcopper and lead sulphides with a soluble phosphate, and subjecting thethus treated pulp to a froth flotation operation in the presence-of asulphide mineral collecting agent, whereby the bulk of th copper thebulkof the lead sulphide.

Preferably the pulpis rendered slightly alkaline after treatment withthe soluble phosphate and before subjecting it to the flotationoperation. 'Ijhis is conveniently, accomplished by rougher concentrate.The cleaner tailing may be returned to the rougher flotation cell forfurther treatment.

The-new method may be applied directly to crushed run-of-mine orescontaining copper sulphides and lead sulphides. Preferably, however, theore is first subjected to a conventional froth flotation operation toreject the bulk of the p sulphide in the pulp is selectively floa edfrom gangue and to produce a concentrate containing the lead and coppersulphide values. The new method advantageously is applied to thetreatadding lime to the phosphate-treated pulp, The pulp preferably isrendered alkaline to a pH ment of the concentrate thus obtained.

In carrying out the new method, the leadcopper concentrate or othermaterial to be treated is incorporated in an aqueous pulp in the usualmanner for conducting froth flotation operations. A quantity of awater-soluble phosphate is added to the pulp. A water-solublesuperphosphate fertilizer, such, for example, as a treble superphosphatefertilizer, is a particularly convenient and inexpensive form of solublephosphate to employ. However, any other water-soluble phosphate may beemployed. The

' method has been carried out successfully using such water-solublephosphates as phosphoric acid, ammonium phosphate, mono-sodiumphosphate, mono-calcium phosphate, and di-sodium phosphate. Generallyspeaking, about 3 to pounds of thewater-soluble phosphate per ton ofmixed sulphides in the .pulp i employedin the conditioning step.

Preferably the pulp is conditioned for a period of several minutes withthe soluble phosphate. This is accomplished by adding the solublephosphate to the pulp and holding the pulp for a conditioning period ofseveral minutes before subjecting it to further treatment.

The phosphate-conditioned pulp preferably is rendered slightly alkalinebefore it is subjected to the flotation operation. The pH of the pulpshould be adjusted to a value above about 8.0,-

advantageously between 8 and 9, after conditioning with the solublephosphate and before subjecting to the flotation operation. It isusually most economical to render the pulp alkaline to the desired pH bythe addition of an appropriate quantity of lime. However, other alkalineagents 1 (such, for example, as caustic soda) may be used addition ofsuiiicient collecting agent and with suflicient agitation and aerationto insure flotaadded. These include a frothing' agent and a collectingagent. Any of the well known frothing agents and any of the commonsulphide mineral collecting agents may be used. For example, thefrothing agent may be pine oil or one of the many available proprietaryfrothing agents, such, for

the trade as Du Pont 3-23" frother. The collecting agent may be any ofthe known sulphide mineral collecting agents used. in frothingcopexample, as the product manufactured by E. I.- -du Pont de Nemours &Company and known to per sulphide ores, such, for example, as a'xanthate. Very satisfactory results have been obtained using sodiumethyl xanthate as the collecting agent, although the invention is not 1limited to the use of this or any other particular in the froth, whereasthe bulk of the lead sulphide is depressed and is withdrawn as the celltailing. The tailings thus constitute the lead concentrate, and thefloated product is the copper concentrate.

In order to. producea lead concentrate containing but little copp r, thefirst or rougher flotation operation may be conducted with the tionof.virtually all of the copper sulphide. Such operation will unavoidablycause some of the lead soluble phosphate and may be subjected to a sec-'0nd or cleaner flotation ,operation to secure a more complete separationof the copper sulphide from the lead sulphide. Usually sufficient of thefrothing and collecting agents remain in the rougher concentrate so thatvery little or none of these reagents need be addedto the pulp for thecleaner operation. The floated concentrate from the cleaner flotationoperation may constitute the flnal copper concentrate, and the tailingsfrom the second or cleaner flotation cell may be discarded as thetailings of the process, or may be returned for retreatment in the flrstor rougher flotation cell for the recovery of the lead and copper whichit contains. Any desired number of flotations intermediate the firstrougher operation and the flnal cleaner operation may of course beemployed.

The following examples illustrate the eiIectiveness of the new process:I

EzampZe IP-An ore concentrate containing a mixture of lead and coppersulphides, assaying 54.96% lead and 10.33% copper, was ground andincorporated in an aqueous pulp for froth flotation. A commercialmono-calcium phosphate fertilizer was added ,to the pulp in the amountof six pounds per ton (the expression pounds per ton as used hereinrefers to the weight of reagent in pounds for each ton of sulphides inthe pulp), and the pulp was allowed to condition in the presence of thephosphate for a period of five minutes. At the end of this conditioningperiod, sufficient lime was added to raise the pH of the pulp to about8.6 to 9.0. The pulp was flotation operation in the presence of afrothing agent and a sulphidemineral collecting agent (sodium ethylxanthate in the amount of 0.1 pound per ton was employed as thecollecting agent). The tailing from this flotation operation constitutedthe lead concentrate. The floated product from this. operation (also inthe form of a flotation pulp) was treated with two pounds per ton of themono-calcium phosphate fertilizer and 0.5 pound per ton of sodiumsilicate, and-the thus treated pulp was subjected to a cleaner flotationoperation. The concentrate from this flotation operation constituted thefinal copper concentrate. The results obtained are set forth in thefollowing table:

Table I Recovery weight Cu Pb CI! -Pb PereentPermltPcreentPianl 10-3554. 100.0 1. 1m 78.1 8-4 21-45 23.7 78.4 1- ms 04.1 13.: n.

Example -2.An ore concentrate containinga mixture of copper and leadsulphides, assaying v tioned pulp was subjected to a rougher froth54.41% lead and 10.44% copper, was conditioned for five minutes with theaddition of nine pounds per ton of a commercial monocalcium phosphatefertilizer. After this conditioning period, the pH of the pulp wasadjusted to 8.6 to 9.0 by the addition of burnt lime. The pulp was thensubjected to a rougher froth flotation operation, using 0.175 pounds perton of sodium ethyl xanthate as the collecting agent. The tailing fromthe rougher operation constituted the lead concentrate. The floatedproduct was treated with 1.5 pounds per ton of the mono-calciumphosphate and was sub-1 jected to a first cleaner froth flotationoperation. The concentrate from this operation was again treatedwith 1.5pounds perton of mono-calcium phosphate, and subjected to a secondcleaner froth flotation operation, with the addition of frothing agentas required. The concentrate from the second cleaner operationconstituted the final copper concentrate. The tailings from the twocleaner operations were combined as the cleaner tailing. The resultsobtained are set forth in the following table:

' Table II g Recovery Weight Cu Pb I Cu Pb Per cent Per cent Per centPer cm! Per c 100.0 10.44 54.41 100.0 100.0 36.7 1.29 79.8 4.6 53.8Copper concentrate. 38.0 2160 17.2 85.6 12.0 Cleaner tail. 25.3 4.0873.5 9.9 34.2

I claim:

1. The method of separating a copper sulphide from a lead sulphide byselective froth flotation which comprises treating an alkaline aqueouspulp of the mixed copper-and lead sulphides with a soluble phosphate,rendering the thus treated pulp slightly alkaline, and subjecting thealkaline pulp to a froth flotation operation in the presence of a coppersulphide collecting agent comprising a xanthate' and selectivelyfloating the bulk of the copper sulphide in the pulp from the bulk ofthe lead sulphide.

2. The method of separating a copper sulphide from a lead sulphide byselectlvefroth flotation which comprises adding a soluble phosphate toan aqueous pulp of the mixed copper and lead sulphides, rendering thepulp alkaline to a pH higher than about 8.0, and subjecting the alkalinepulp to a froth flotation operation in'the presenceof a copper sulphidecollecting agent comprising a xanthate and selectively floating the bulkof the copper sulphide in the'pulp from the bulk of the lead sulphide.

.3. The method of separating a copper sulphide from a lead sulphide byselective froth flotation which comprises conditioning an aqueous pulpcontaining the mixed copper and lead sulphides with a. soluble phosphatefor a period of several utes, then rendering the pulpslightly alkaline,and subjecting the alkaline pulp to a froth flotation operation in thepresence of a copper sulphide collecting ent comprising a xanthate -'1:selectively floating the bulk of the: copper sulphide'in the. pulp fromthe bulk of the lead sulphide.

4. The method of separating a copper sulphide from a leadsulphide byselective froth flotation which comprises conditioning an aqueous pulpcontaining the mixed copper and lead sulphides with a soluble phosphatefor a period of several minutes, then rendering the pulp alkaline to apH of about 8 to 9, and subjecting the alkaline pulp to a frothflotation operation in the presence of a copper sulphide collectingagent comprising a xantha-te and selectively floating the bulk of mecopper sulphide in the pulp from the bulk of the lead sulphide.

5. The method of separating a copper sulphide from a lead sulphide byselective froth flotation which comprises treating an aqueous pulp ofthe mixed copper and lead sulphides with a soluble phosphate, addinglime to the thus treated pulp to render it alkaline to a pH higher thanabout 8.0, andlsubjecting the alkaline pulp to a 'f-roth flotationoperation in the presence of a xanthate collecting agent and selectivelyfloating the bulk of the copper sulphide in the pulp from. the bulk ofthe lead sulphide. a

6. The method .of separating a copper sulphide from a lead sulphide byselective froth flotation which comprises treating an aqueous pulp ofthe mixed copper and lead sulphides with a superphosphate, rendering thethus treated pulp slightly alkaline, and subjecting the alkaline pulp toa froth flotation operation in the presence of a xanthate collectingagent and selectively floating the bulk of" the copper sulphide in thepulp from the bulk of the lead sulphide.

- aqueous pulp containing the mixed copper and tively floating the bulkof the. copper sulphide ln' the pulp from the bulk of the lead sulphide.

lead minerals with about 3 11015 pounds of a superphosphate per ton ofmixed sulphides for a period of several minutes, rendering the pulpalkaline with lime to a pH of about 8 to 9, and subjecting the alkalinepulp to a froth flotation operation in the presence of a copper sulphidecollecting agent comprising a xanthate and selec- 8. The method ofseparating a copper sulphide from alead sulphide by selective frothflotation which comprises treating an aqueous pulp of the mixed copperand lead sulphides with a soluble .phosphate, rendering the thus treatedpulp slightly alkaline, subjecting the alkaline pulp to a'igougher frothflotation operation in the presence of a xanthate collecting agent andselectively floating a tailing containing the bulk of the lead sulphid'ewith but little of the copper sulphide and 'a concentrate containing thebulk of the copper sulphide together with some of the lead sulphide,treating said concentrate with a further quantity of a solublephosphate, and subjecting the thus treated concentrate to a cleanerfroth flotation operation in the presence ,of a xanthate collectingagent and selectively floatin a concentrate containing the bulk of thecopper sulphide with but little lead sulphide.

KURT FEHX RUCKWARDT.

